From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail105.syd.optusnet.com.au ([211.29.132.249]:53362 "EHLO mail105.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730419AbfHAV4T (ORCPT ); Thu, 1 Aug 2019 17:56:19 -0400 Date: Fri, 2 Aug 2019 07:55:08 +1000 From: Dave Chinner Subject: Re: [PATCH] fs: xfs: xfs_log: Don't use KM_MAYFAIL at xfs_log_reserve(). Message-ID: <20190801215508.GN7777@dread.disaster.area> References: <20190729215657.GI7777@dread.disaster.area> <1564653995-9004-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20190801185057.GT30113@42.do-not-panic.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Tetsuo Handa Cc: Luis Chamberlain , linux-xfs@vger.kernel.org, Brian Foster On Fri, Aug 02, 2019 at 06:13:12AM +0900, Tetsuo Handa wrote: > On 2019/08/02 3:50, Luis Chamberlain wrote: > > That's quite an opaque commit log for what started off as a severe email > > thread of potential leak of information. As such, can you expand on this > > commit log considerably to explain the situation a bit better? Your > > initial thread here provided much clearer evidence of the issue. As-is > > this commit log tells the reader *nothing* about the potential harm in > > not applying this patch. > > > > You had mentioned you identified this issue present on at least > > 4.18 till 5.3-rc1. So, I'm at least inclined to consider this for > > stable for at least v4.19. > > > > However, what about older kernels? Now that you have identified > > a fix, were the flag changed in prior commits, is it a regression > > that perhaps added KM_MAYFAIL at some point? > > I only checked 4.18+ so that RHEL8 will backport this patch. According to > Brian Foster, commit eb01c9cd87 ("[XFS] Remove the xlog_ticket allocator") > ( https://git.kernel.org/linus/eb01c9cd87 ) which dates back to April 2008 > added KM_MAYFAIL flag for this allocation > > - buf = (xfs_caddr_t) kmem_zalloc(PAGE_SIZE, KM_SLEEP); > + tic = kmem_zone_zalloc(xfs_log_ticket_zone, KM_SLEEP|KM_MAYFAIL); > > though Dave Chinner thinks that the log ticket rework is irrelevant. > Do we need to find which commit made this problem visible? No. -Dave. -- Dave Chinner david@fromorbit.com